Complementary output buffers may be used in devices such as the Universal Serial Bus. Conventional approaches to presenting a complementary differential output include implementing two separate differential output drivers. Referring to FIG. 1, an output driver 10 is shown receiving an input signal IN and an output driver 12 is shown receiving an input signal INB. The output driver 10 presents a signal A and the output driver 12 presents a signal B. The output drivers 10 and 12 provide a complementary differential output. Since the output driver 10 and the output driver 12 operate independently, it is difficult to inherently match the outputs. Additionally, it may be impractical to produce two sets of output buffers that operate over a wide load and signal swing such as a Universal Serial Bus device.
The output driver 10 is required to provide rising edge circuitry to present the signal A that matches the falling edge circuitry of the output driver 12 to present the signal B. The implementation of separate circuitry results in poor control of parameters like the crossover voltage of the signal A and the signal B and the rise-time/fall-time ratio.
Another solution would be to implement the output drivers 10 and 12 using operational amplifiers. However, operational amplifier drivers are difficult to design to handle large loads with sufficient bandwidth to operate with Universal Serial Bus devices. Additionally, operational amplifier devices may be difficult to design to operate over a wide output swing with a low voltage operation.